East Sussex Fire and Rescue Service were called at 17.13 to reports of a fire in Brighton.
A five-storey, terraced building on Compton Avenue was alight.
Four appliances attended the scene and firefighters used breathing apparatus, firefighting foam and main jets to tackle the fire.
The incident is now being scaled down, with two fire engines remaining at the address.
A fire investigation will be carried out.
There are no reports of injuries.